Pima Indians have been shown to have a high prevalence of diabetes mellitus and hyperinsulinemia. Despite these the Pimas have greatly decreased incidence of cardiovascular disease. Studies of plasma lipids have shown that total serum cholesterol values are low, and they do not increase with age. Plasma LDL levels are low and LDL synthetic rates were shown to be decreased. VLDL metabolism in Pima Indians will be investigated in order to study the relationship between VLDL and the other serum lipoprotein classes and to determine the effect of hyperinsulinism on VLDL metabolism. Synthetic and catabolic rates for VLDL will be compared in groups having different insulin levels using tritiated glycerol as a precursor. Conversion of VLDL to LDL will be studied using 125I VLDL and 131I LDL simultaneously. In addition plasma free fatty acid levels and turnover rates will be assessed to determine if free fatty acid production correlates with serum insulin values or triglyceride production. The results of this study should yield data on VLDL metabolism and its conversion to LDL in this population and explore the relation between these lipoproteins and cardiovascular disease.